I don't know of any definitive study other than "tribal lore" that says to use larger media for a smoother surface because the depth of the dent is much less. A small media impact must drive itself very deep in order to achieve the intensity level you desire. Substituting larger media (more mass, larger impact diameter) will create a shallow dent but with deep compression. You should experiment with scrap pieces until you get the size you need.
You should also search or library using various search terms such as dent, depth, shot size, surface roughness etc.
